Load/re-load families from folder and overwrite in Model

Hi everyone,

I’m try to create a script for family manager. I have a different main families e a lot of nested families. I want to create a script which I can load or reload and overwrite nested families (which I select) from a folder in main families.
How can I make it?
I would like to make it in batch.

I start with this script but it don’t overwrite families.